/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.sdk.io.kinesis;



import java.util.NoSuchElementException;

import java.util.Objects;



/**

 * Similar to Guava {@code Optional}, but throws {@link NoSuchElementException} for missing element.

 */

abstract class CustomOptional<T> {



  @SuppressWarnings("unchecked")

  public static <T> CustomOptional<T> absent() {

    return (Absent<T>) Absent.INSTANCE;

  }



  public static <T> CustomOptional<T> of(T v) {

    return new Present<>(v);

  }



  public abstract boolean isPresent();



  public abstract T get();



  private static class Present<T> extends CustomOptional<T> {



    private final T value;



    private Present(T value) {

      this.value = value;

    }



    @Override

    public boolean isPresent() {

      return true;

    }



    @Override

    public T get() {

      return value;

    }



    @Override

    public boolean equals(Object o) {

      if (!(o instanceof Present)) {

        return false;

      }



      Present<?> present = (Present<?>) o;

      return Objects.equals(value, present.value);

    }



    @Override

    public int hashCode() {

      return Objects.hash(value);

    }

  }



  private static class Absent<T> extends CustomOptional<T> {



    private static final Absent<Object> INSTANCE = new Absent<>();



    private Absent() {}



    @Override

    public boolean isPresent() {

      return false;

    }



    @Override

    public T get() {

      throw new NoSuchElementException();

    }



    @Override

    public boolean equals(Object o) {

      return o instanceof Absent;

    }



    @Override

    public int hashCode() {

      return 0;

    }

  }

}